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brep structure of cylinder

Posted: Wed Sep 04, 2019 4:38 am
by Sergio Trastevere

I have loaded a .brep file I created in opencascade - based application. Particularly brep structure seems to be different on open cylinders (non-solid shell with a single face). The old app shows a single wire but in dg kernel I am getting two wires.

Can anybody shed a light on this please?

Re: brep structure of cylinder

Posted: Thu Sep 05, 2019 7:14 am
by nickz
Hello Sergio
DGK removes seam edges from the cylinder's faces on load. It is the way we do it. This should not create any problems. Seam edges are unnatural, unnecessary and confusing in our view.

Seam edges are the two geometrically coinciding edges going in opposite direction. They are added by some software to make cylindrical surface a rectangular curved patch joined by two edges (seams) to form closed surface. This way the face has a single wire with four edges.

DGK goes another way, used by many software also: We model it as a single face with two isolated wires with a single edge in each.

As you know, surface in BRep can be represented in many ways. It is similar to mesh. Same surface can be meshed in various ways


Re: brep structure of cylinder

Posted: Fri Sep 06, 2019 1:02 am
by Sergio Trastevere
Thank you, Nick